Process for producing semiconductive porcelain composition and heater employing semiconductive porcelain composition

Abstract

To improve jump characteristic of BaTiO 3 —(Bi 1/2 Na 1/2 )TiO 3 material. There is provided a process for producing a semiconductive porcelain composition in which a part of Ba is substituted with Bi—Na, the process including a step of preparing a (BaQ)TiO 3 calcined powder (in which Q is a semiconductor dopant), a step of preparing a (BiNa)TiO 3 calcined powder, a step of mixing the (BaQ)TiO 3 calcined powder and the (BiNa)TiO 3 calcined powder, a step of molding and sintering the mixed calcined powder, and a step of heat-treating the obtained sintered body at 600° C. or lower; and a PCT heater employing the element prepared by the above steps.

The invention claimed is: 
     
       1. A process for producing a semiconductive porcelain composition provided with an electrode in which the semiconductive porcelain composition is a BaTiO 3 -based semiconductive porcelain composition free of Pb, in which a part of Ba of BaTiO 3  is substituted with Bi—Na, and having a positive temperature coefficient of resistance, the process comprising:
 a step of preparing a (BaQ)TiO 3  calcined powder (wherein Q is a semiconductor dopant); 
 a step of preparing a (BiNa)TiO 3  calcined powder; 
 a step of mixing the (BaQ)TiO 3  calcined powder and the (BiNa)TiO 3  calcined powder; 
 a step of molding and sintering the mixed calcined powder; 
 a step of heat-treating said obtained sintered body at 600° C. or lower for 1 hour or more in an atmosphere containing oxygen or in the air; and 
 a step of forming the electrode to said obtained sintered body. 
 
     
     
       2. The process for producing a semiconductive porcelain composition according to  claim 1 , wherein the step of forming the electrode to said obtained sintered body is conducted, and then the step of heat-treating said obtained sintered body is conducted. 
     
     
       3. The process for producing a semiconductive porcelain composition according to  claim 1 , wherein sintering is conducted in the air, a reducing atmosphere or an inert gas atmosphere of low oxygen concentration at a sintering temperature of from 1,200° C. to 1,400° C. 
     
     
       4. The process for producing a semiconductive porcelain composition according to  claim 2 , wherein sintering is conducted in the air, a reducing atmosphere or an inert gas atmosphere of low oxygen concentration at a sintering temperature of from 1,200° C. to 1,400° C. 
     
     
       5. A heater comprising a heating element comprising a semiconductive porcelain composition provided with an electrode, which is obtained by forming the electrode to the semiconductive porcelain composition obtained by the production process according to  claim 1 . 
     
     
       6. A heater comprising a heating element comprising a semiconductive porcelain composition provided with an electrode, which is obtained by forming the electrode to the semiconductive porcelain composition obtained by the production process according to  claim 2 . 
     
     
       7. A heater comprising a heating element comprising a semiconductive porcelain composition provided with an electrode, which is obtained by forming the electrode to the semiconductive porcelain composition obtained by the production process according to  claim 3 . 
     
     
       8. A heater comprising a heating element comprising a semiconductive porcelain composition provided with an electrode, which is obtained by forming the electrode to the semiconductive porcelain composition obtained by the production process according to  claim 4 .